Parts of the Midwest are bracing for their coldest temperatures in decades this week, with Tuesday night conditions predicted to feel like 50 degrees below zero or colder in areas of the Dakotas, Minnesota and Iowa, according to AccuWeather.
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SHEBOYGAN - As temperatures reach brutal lows this week, we want to make sure Wisconsinites are prepared for the coming once-in-a-generation cold.

We spoke to Dr. Michael DeFrank, emergency medicine physician at HSHS St. Vincent Hospital in Green Bay, about what extremely cold temperatures do to the body. His responses are summarized for conciseness.

Q: What does frostbite look like?

A: Frostbite can look like anything from just red, pink skin to actually mummified tissue if it's really, really bad a couple weeks after injury.

The kind of frostnip and frostbite you'd get after being outside too long shoveling or playing in the snow or skiing would be just kind of pink skin. Let's say you were exposed and got stuck outside and your car got stuck a little longer than you thought, you might get some clear blisters on your skin. If it were really bad, you'd get what we call hemorrhagic blisters where you'd actually have some blood underneath the tissue or the tissue might look black, almost like a burn.

But if it's severe — let's say you had too much to drink and you passed out and your toes got super cold and actually had ice form under your skin, you get what we call mummification, which would look like almost dried out skin and a toe or into the foot might fall off weeks later.

Historically cold weather is expected to chill much of the country this week thanks to a polar vortex.(Photo11: AccuWeather.com)

Q: Have you seen a lot of it?

A: Locally a little. Over my career, because that's been almost 20 years, I've seen quite a bit. We live in Wisconsin so most people are pretty smart, but occasionally when I work nights we do get people who stay outside too long or have had too much to drink and don't have the sense to get inside and we have seen a few cases of that lately.

Q: How long can you be outside in minus 50 degree windchill?

A: That depends on a lot of different things. It depends on the wind and how much skin is exposed and how much blood flow you have to the end of your digits and then what kind of other medication you're on — if you're on anything that can accelerate frostbite or reduce blood flow to the tissues. If we're talking about hypothermia, it's a little different. Usually you don't want to expose skin for more than five or 10 minutes on bad days like that. Or even less than that because the wind obviously makes the cold that much worse, taking the heat off the skin. Less than five minutes can develop a significant frostbite injury.

Q: If you weren't wearing a coat, how long would it take to get hypothermia or frostbite compared to if you were wearing a coat?

A: Again, it's multi-factorial. It depends on how healthy you are to begin with and then the temperature and then how much wind. The wind causes convection so that removes the heat quicker. Let's say if you're diabetic and have a blood flow problem already to your extremities or if you've consumed a great deal of alcohol. With alcohol your blood is shunted to your skin so all the core blood that would keep you warm is now on your skin, which makes you feel good but drains your body temperature that much quicker. Someone like that can develop moderate to severe hypothermia in even 30 minutes outside without enough insulation.

The National Weather Service's Wind Chill Chart shows how quickly it becomes dangerous to be outside in cold temperatures.(Photo11: Courtesy of the National Weather Service)

Q: What exactly happens to your internal organs during hypothermia?

A: You get lower blood pressure, lower cardiac output, you get less blood flow to your brain and heart, which require the most oxygen-rich blood and are susceptible to injury even for a few minutes without appropriate circulation.

In very severe cases, you get crystal formation in your tissue if you have severe hypothermia and that leads eventually to death. It's from the outside in. Your body is very sensitive to changes in temperature so as your temperature drops, your body is less able to deal with the fluctuations in your pH and some of the byproducts of metabolism. And then as you become colder you're not able to clear those out via your kidneys as your metabolic rate slows. As your metabolic rate slows your brain doesn't get enough blood, nor does your heart. And that's eventually what leads to death — the poor cardiac output and poor circulation due to changes in your temperature.

Your body is only able to compensate down to (body temperatures of) 90 to 92 degrees, and then you start losing your ability to regulate your temperature after that. Once you get below 90 to 92 degrees, you can't shiver anymore, you can't warm yourself anymore. Your body can't do things to preserve itself.

Q: Can your skin recover from frostbite?

A: It can recover from a first-degree frostbite or frostnip and a second degree would be almost like a burn. But when you talk third and fourth degree, believe it or not it's a lot like burn care. If you get into third and fourth degree, a lot of times you're talking about tissue loss and amputation.

Q: Are there different degrees of frostbite? Does only the worst frostbite turn black?

A: It's marked a lot like a burn injury. I think the grading's very similar. First and second degree are superficial, just involving the very outer layers of the skin, but when we're talking about a full thickness injury to the digit that usually means that there's a complete loss of blood flow and ice crystal formation. That usually means you're going to lose it. First and second degree would be like local wound care. Third degree would almost be like the burn, where you would need grafting and tissue excision.The worst frostbite turns black. That's a fourth degree.

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Take a look at what a polar vortex is and why it causes such bitter cold temperatures.
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Q: Is there an increased risk for heart attack in the extreme cold?

A: There is some suggestion that you release, under stressful situations including hypothermia, factors that can increase your risk for having blood clots in your arteries. They're stress hormones that raise your risk of having a heart attack or a stroke. But it's really exacerbated by physical activity like shoveling and stuff like that. It's not just the cold, but people shoveling in their 60s and 70s. Exertional activity plus the stress hormones is a bad combination. The stress hormones and some of the clotting hormones that get secreted when you get cold, that really raises your risk of forming a blood clot.

Obviously, if you're having any cardiac or anginal symptoms, you should stop what you're doing. If you have a history of any coronary disease, you probably should be blowing the snow, not shoveling it, or having somebody else do it for you. Symptoms of angina are nausea, jaw pain, chest pain, shortness of breath, arm pain. If you feel any of that, it's time to put down the shovel right away.

Q: What else should we know?

A: A lot of the severe hypothermia we see up here is because people aren't using their brains. They're outside too long or they're overconfident or a lot of them have consumed alcohol. So, A, they're not using their right mind and, B, when you drink alcohol, you feel flushed because your blood goes to your skin and your body's mechanism to preserve heat is just the opposite of that — to keep the blood inside.

We say in medicine, particularly emergency medicine, "Temperature sensation is only skin deep." So you may feel cold but your core is OK. And when you drink alcohol, it's just the opposite. You may feel OK but your core temp is draining.